1. Revised tholin profile for the atmosphere of Titan
Mao-Chang Liang1, J. A. Kammer, X. Zhang3, D. Shemansky4, Y. L. Yung2
1 Research Center for Environmental Change, Academia Sinica
2 Division of Geological and Planetary Sciences, California Institute of Technology
3 University of Arizona
4 Space Environment Technologies

2. Lorenz + Mitton 2002

3. Solar Scattering
Stellar Occultation
J. Ajello

4. Cassini UVIS Stellar occultations Solar occultation
Aerosol extinction profiles
Tb  Vi, Tb  Sco, T21  Eri, T41  CMa (ingress & egress), T47  Uma
Solar occultation T0
Scattering spectrum at 1040 km
Tholin retrieved for A, using Khare et al. aerosols

5. T0 solar reflection spectrum
High resolution slit; Integration time sec;
Red line: Effective altitude 1040 km; mid pixel 1203 km
Green line: Effective altitude 1612 km
Cyan line: best fitting model spectrum

6. TB UVIS extinction spectrum
tholin
CH4
Impact: 514 km
Liang et al. 2007

7. UVIS extinction profiles

8. Modeling – No production/loss
10-15 g cm-2 s-1
10-4 g cm-3
D~1.3
10-3 g cm-3
D~1.5
~10-4 g cm-3
76 A -> ~300 A
Fractal dimension 1.5
76 A
76 A -> ~500 A
76 A
eddy

9. Extinction coefficient (Mie + Khare et al.)
Extinction not sensitive to fractal dimension but scattering does
Particle radius (A)

10. Solution #1 – C2H2 -> tholin
310-15
g cm-2 s-1
10-15 g cm-2 s-1
size increase
76 A -> ~500 A
310-15
g cm-2 s-1

11. Solution #2 – C6N2 -> tholin
~210-15
g cm-2 s-1
Psat(C6N2)
Liang et al. (2007)

12. Lavvas et al. (2011) model Lavvas et al. UVIS T41 UVIS T0 310-14
g cm-2 s-1
D~3
UVIS T0
Lavvas et al.
UVIS T41

13. Fractal particles Aggregate of molecules at ~1000 km UVIS at ~400 km
monomer: 8 A
Mie radius: 76 A
density: ~10-4 g cm-3
-> fractal dimension: ~1.3
UVIS at ~400 km
size increase to ~50 nm
ISS at ~520 km
size ~40 nm
fractal dimension <2
Main haze (<300 km)
monomer: 66 nm
fractal dimension: 2

14. Summary Low density fractal particle Particle size of 76 A at 1040 km
~10-4 g cm-3 above ~800 km
Particle size of 76 A at 1040 km
Increase to ~500 A below ~400 km, compared to 660 A monomer size below 300 km
Mass flux from the top is ~10-15 g cm-2